1. Field of the Invention
This invention relates generally to compositions, methods and apparatus for use in the manufacture of semiconductor, photovoltaic, LCD-TFT, or flat panel type devices. More specifically, the invention relates to methods and compositions for depositing ternary oxide films on a substrate.
2. Background of the Invention
As the design and manufacturing of semiconductor devices continues to evolve, the semiconductor industry is constantly seeking new and novel methods of depositing films onto substrates, such that the resulting film will have certain sought after properties. One example of these properties can be found in metal electrodes to be employed in advanced CMOS technologies together with high-k dielectric films. For the next generation nodes, ruthenium is considered as the best candidate for electrode for FeRAM and DRAM applications, and potentially for MRAM. One reason for this is that the resistibility of ruthenium is lower than iridium and platinum. Additionally, even RuO2 has better conductivity than the two corresponding metal oxides in the case where a metal layer is in contact with high-k layers. Recent researches mentioned the use of ruthenium-based materials, CaRuO3, SrRuO3 and BaRuO3, as an electrode for ferroelectric applications. Ternary oxicdes such as ARuO3 (A=Ca, Sr and Ba) complexes show perovskite crystal structure and could be grown epitaxially on several types of insulation oxide layers. Hence, it is thought that ARuO3 films may be suitable to be deposited on gate stack structures. Furthermore, such films have suitable metallic conductivity.
As the size of chip becomes smaller and smaller, each layer deposited thereon should be thinner and thinner, making deposition techniques such as chemical vapor deposition (CVD) or atomic layer deposition (ALD) desirable to deposit these layers.
A large variety of Ru precursors are available and many have been studied in CVD or ALD mode. However, most of them have recurrent drawbacks: low vapor pressure (e.g. 0.25 Torr at 85° C. for Ru(EtCp)2), high impurity contents of the obtained films (e.g. carbon and oxygen in most of the cases), long incubation time, poor adherence, and non-uniformity in deep trenches.
In some cases, precursors are not liquid and need to be dissolved in a solvent or mixture of solvents to allow an easy delivery of the vapors to the reaction chamber Moreover, the solvents that are used are usually toxic and/or flammable and their usage brings many constraints (safety aspects, environmental issues). Besides, the use of precursors with melting points higher than 20° C. implies many additional constraints during the process deposition (heating of the delivery lines to avoid condensation of the precursor at undesired locations) and during the transportation.
The number of known strontium and barium precursors available for vapor deposition is low compared to ruthenium. Many strontium and barium precursor are solid with a high melting point (above 200° C.), and their vapor pressure is low, which generates throughput and equipment issues. Stability may also a problem because the temperature at which the precursor reacts with an oxidizing agent corresponds to its decomposition temperature.
Consequently, there exists a need for ruthenium precursors with good reactivity and incubation time properties, which can be combined with alkali earth metal precursors which have a melting point less than about 200° C. to form ternary oxide films, and which precursors may be dissolved in a suitable solvent to aid in the deposition process.